The present invention is generally directed to display panels and in particular to display panels using flexible substrates such as plastic film and processes for their production. A display panel, as used herein, is a pair of substrates having a display medium sandwiched therebetween which is controlled by an applied electric current, voltage, magnetism or other force. Examples of display panels include liquid crystal display panels, electrochromic display panels, EL(electroluminescence) display panels, electrophoretic display panels, magnetic display panels and others. The display medium sandwiched between the pair of substrates is not limited to a single layer but may have multiple layers as well. To avoid unnecessary repetition the description will be primarily directed to liquid crystal display panels although the invention is equally applicable to other types of display panels as noted above.
Various known methods exist for the production of flexible display panels for use with liquid crystals, by using plastic films. When a theremosetting epoxy resin, conventionally used with glass substrates is used on flexible plastic film substrates the weak adhesion of the thermosetting epoxy resin to the plastic substrate, caused, for example, by a lack of flexibility of the resin, causes the resin to peel off during the processing. This is particularly so where simultaneous construction of a plurality of panels using large substrates which are then cut into smaller, appropriate sizes is performed. As a result the reliability of these flexible display panels is particularly low.
On the other hand, where flexible adhesives having a high peel strength, such as silicon or urethane type adhesives are used other disadvantages are present. The silicon type adhesive has both a high gas and vapor permeability and tends to result in bubbles in the liquid crystal layer in a durability test. The urethane type adhesive causes the display panel to have a short service life, e.g., a liquid crystal display, since a urethane type adhesive tends to have a large reactive influence on the liquid crystal composition.
Accordingly, there is a need for a display panel composed of flexible substrate which has a long service life and is able to reliably survive bending of the display panel, e.g. a liquid crystal using flexible bases such as plastic bases and also to improve the production thereof.